netdev - Re: Regarding bottlenecks for high speed packet generation

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Date:	Thu, 25 Oct 2012 21:39:46 +0200
From:	Daniel Borkmann <danborkmann@...earbox.net>
To:	Ajith Adapa <adapa.ajith@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Regarding bottlenecks for high speed packet generation

(Please reply to all, so that also netdev gets CC'ed as well.)

On Thu, Oct 25, 2012 at 8:25 PM, Ajith Adapa <adapa.ajith@...il.com> wrote:
>> Actually in my experience not. On Gigabit Ethernet (depending on your
>> machine) you should be able to generate about 80k pps with 1500 byte
>> (e.g. with netsniff-ng's trafgen) having the default tc discipline.
>>
> Currently I can see that my machine is able to generate 80MBytes/sec
> for 1500 byte packets with
> default tc discipline. Its a simple desktop with i5 dual core machine, 4GB RAM.

Hmm, what is the interconnect of the NIC? PCIe? I've seen some _PCI_
devices on simple desktop machines where this number could fit.

>> Have you looked how much pps the kernel space pktgen can generate on
>> your machine with 1500 byte packets?
>>
>> What tool do you use to measure this reported rate? Do you analyze
>> driver statistics from e.g. procfs, or do you use a libpcap-based tool
>> to measure the stuff (which you shouldn't since it could falsify your
>> stats)? How was your measurement setup?
>
> Currently I am using IXIA for the destination to confirm the numbers
> and also basic stats from system monitor.

Ok.

> I have tried pktgen quite long back but I could make a try and confirm
> the rate at which generates on my machine.

Yes, might be worth a try.

> When I tried powertop tool I see that out of list processes who
> consume more amount of power I can see that the NIC interface
> on which I am trying to burst the traffic is consuming around 63% with
> interrupts. But does the NIC card drop a interrupt for
> every packet which it has successfully sent ?

If the driver uses NAPI [1] / the chip supports that, then not. You
can observe the hardware / software interrupts via ifpps or watching
procfs or some other tools, or simply look at the driver
implementation.

[1] http://www.linuxfoundation.org/collaborate/workgroups/networking/napi
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